obslog: add a patch option Add support for '--patch' option in obslog for a similar effect than "hg log --patch". The patch support is only limited to a few basic cases that will be extended in the future.

obslog: clarify some sorting code I'm not sure why Boris did it, but this belong to the next patch.

obslog: pass directly unfiltered_repo _debugobshistorydisplaynode used to create two times an unfiltered repo, makes _debugobshistoryrevs create only one unfiltered repo and pass it directly.